Use of alkenylsuccinic acid half-amides as anti-corrosion agents

ABSTRACT

The use, as anti-corrosion agents, of alkenylsuccinic acid half-amides of the formulae   &lt;IMAGE&gt;   in which R denotes C6-C18-alkenyl, R1 denotes C12-C18-alkyl and K denotes a proton, an alkali metal ion or an ammonium ion of the formula NHR2R3R4, and R2, R3 and R4 are identical or different and denote hydrogen, C1-C12-alkyl, 2-hydroxyethyl or 2-hydroxypropyl.

The use of salts of alkenylsuccinic acid half-amides of the formulae ##STR2## in which R denotes C₆ -C₁₈ -alkenyl and R¹ and R² denote hydrogen or C₁ -C₁₀ -alkyl as anti-corrosion agents in aqueous systems is already known (German Pat. Nos. 3,300,874, 3,319,183 and 3,341,013). Although these compounds display a very good anti-corrosion action in aqueous metal working fluids free from mineral oil, they are frequently unsuitable for use in formulations containing mineral oils, since these compounds are not soluble, or are not sufficiently soluble, in mineral oil. This results in a separation of the mineral oil emulsions into an aqueous phase and an oil-containing phase, and the use value of these compounds is therefore greatly restricted.

It has now been found that these disadvantages of the known alkenylsuccinic acid half-amides can be avoided if the amide group is substituted by a C₁₂ -C₁₈ -alkyl radical. The invention relates to the use, as anti-corrosion agents, of alkenylsuccinic acid half-amides of the formulae ##STR3## in which R denotes C₆ -C₁₈ -alkenyl, preferably C₉ -C₁₂ -alkenyl, R¹ denotes C₁₂ -C₁₈ -alkyl, preferably C₁₂ -C₁₄ -alkyl, and K denotes a proton, an alkali metal ion or an ammonium ion of the formula NHR² R³ R⁴ and R², R³ and R⁴ are identical or different and denote hydrogen, C₁ -C₁₂ -alkyl, 2-hydroxyethyl or 2-hydroxypropyl.

The preparation of the alkenylsuccinic acid half-amides is carried out in a known manner by heating an alkenylsuccinic anhydride with an amine of the formula NH₂ R¹ in an approximately equimolar ratio for approx. 2 hours at 70° to 90° C. The compounds obtained thereby can be employed without further treatment, i.e. in the form of the free acid, as anti-corrosion agents in metal working fluids. It is preferable, however, to use these alkenylsuccinic acid half-amides in the form of their alkali metal or alkanolamine salts. These salts can be prepared in a simple manner by neutralizing the alkenylsuccinic acid half-amides, for example by neutralization with sodium hydroxide solution, monoethanolamine, diethanolamine or triethanolamine.

The alkenylsuccinic acid half-amides described above can be employed with particular advantage as anti-corrosion agents in aqueous cooling lubricants and cooling lubricants containing mineral oil, in particular drilling, cutting and rolling fluids. These cooling lubricants are prepared by stirring the reaction products into the required amount of water or mineral oil. The concentration used in the drilling, cutting and rolling fluids is generally about 0.1 to 10% by weight, preferably 2 to 5% by weight. If necessary, it is also possible to add further active compounds which are known for this end use.

Depending on the amount of mineral oil, the alkenylsuccinic acid half-amides described produce clear or milky, emulsion-like fluids which retain their good properties in use over a fairly long period of time, since no creaming or phase separation takes place even after several days.

The following examples illustrate the invention; the subsequent tables 1 to 3 show the excellent properties of the products compared with the comparison substances A and B.

EXAMPLE 1 N-coconut-alkyltripropenylsuccinic acid half-amide

197 g (1 mol) of coconut oil amine are placed in a reaction flask and 224 g (1 mol) of tripropenylsuccinic anhydride are added dropwise, with stirring. In the course of this the temperature rises rapidly. The internal temperature is kept between 70° and 90° C. by cooling with a water-bath. When the dropwise addition is complete, the mixture is stirred for a further 90 minutes at 80° C. and is then allowed to cool to room temperature. Approx. 420 g of a viscous liquid having an acid number of approx. 130 (theory: 133.3) are obtained.

EXAMPLE 2 N-dodecyltetrapropenylsuccinic acid half-amide

266 g (1 mol) of tetrapropenylsuccinic anhydride are added dropwise to 185 g (1 mol) of dodecylamine, and the procedure of Example 1 is followed. Approx. 450 g of a viscous liquid having an acid number of approx. 125 (theory: 124.4) are obtained.

EXAMPLE 3 N-(dodecyl/tetradecyl)-tripropenylsuccinic acid half-amide

196 g of a mixture of dodecylamine and tetradecylamine (molar ratio 75:25) are initially taken at room temperature, 224 g (1 mol) of tripropenylsuccinic anhydride are added dropwise, with stirring, and the further procedure is as in Example 1. Approx. 420 g of a viscous liquid having an acid number of approx. 130 (theory: 133.6) are obtained.

COMPARISON SUBSTANCE A N-butyltripropenylsuccinic acid half-amide

72 g (1 mol) of n-butylamine are initially taken and 224 g (1 mol) of tripropenylsuccinic anhydride are added dropwise at such a rate that the internal temperature does not exceed 80° C. When the dropwise addition is complete, the mixture is stirred for a further 30 minutes at 80° C. and is then allowed to cool. Approx. 295 g of a viscous liquid having an acid number of approx. 190 (theory: 189.5) are obtained.

COMPARISON SUBSTANCE B N,N-dioctyltripropenylsuccinic acid half-amide

250 g (1 mol) of dioctylamine are initially taken at room temperature. 224 g (1 mol) of tripropenylsuccinic anhydride are added dropwise, with stirring, in the course of which the temperature rises to 80° C. When the dropwise addition is complete, the mixture is stirred for a further 21/2 hours at 80° C. and is then allowed to cool. Approx. 470 g of a viscous liquid having an acid number of approx. 120 (theory: 118) are obtained.

                                      TABLE 1                                      __________________________________________________________________________     Formulation/example                                                                           1      2      3      A      B                                   __________________________________________________________________________     Product according to example                                                                  44.1 g 45.6 g 43.0 g 25.4 g 57.2 g                              Triethanolamine                                                                               40.9 g 39.4 g 42.0 g 59.6 g 37.8 g                              Distilled water                                                                               15.0 g 15.0 g 15.0 g 15.0 g 15.0 g                              Appearance at 20° C.                                                                   clear, clear, cloudy clear, cloudy,                                            liquid liquid        liquid separates                           SOLUBILITY IN H.sub.2 O                                                        3% strength in distilled H.sub.2 O                                             --   immediately                                                                              clear  clear  clear  transparent                                                                           transparent                         --   after 24 hours                                                                           unchanged                                                                             unchanged                                                                             unchanged                                                                             cloudy cloudy                              pH value       9.3    9.3    9.2    9.4    9.5                                 1% strength in distilled H.sub.2 O                                             CORROSION RESISTANCE                                                           Herbert Test                                                                             0.5% trace of rust                                                                         considerable                                                                          considerable                                                                          considerable                                                                          considerable                        DIN 51360/1           rust   rust   rust   rust                                          1.0% no rust                                                                               trace of                                                                              trace of                                                                              rust   considerable                                              rust   rust          rust                                          2.0% no rust                                                                               no rust                                                                               no rust                                                                               no rust                                                                               no rust                             Filter paper test                                                                        1.0% rust   rust   rust   considerable                                                                          considerable                        DIN 51,360/2                        rust   rust                                          2.0% no rust                                                                               trace of                                                                              trace of                                                                              rust   rust                                                      rust   rust                                                        2.5% no rust                                                                               trace of                                                                              no rust                                                                               no rust                                                                               no rust                                                   rust                                                     __________________________________________________________________________

                                      TABLE 2                                      __________________________________________________________________________     Formulation/example                                                                           1     2    3    A      B                                        __________________________________________________________________________     Product according to example                                                                  80 g  80 g 80 g 66 g   81 g                                     Triethanolamine                                                                               5 g   5 g  5 g  15 g   4 g                                      Sodium hydroxide solution,                                                                    15 g  15 g 15 g 19 g   15 g                                     40% strength                                                                   Appearance at 20° C.                                                                   clear,                                                                               clear,                                                                              clear,                                                                              milky, clear,                                                  liquid                                                                               liquid                                                                              liquid                                                                              cloudy liquid                                   Solubility, 3% strength                                                        in distilled H.sub.2 O                                                         immediately    clear clear                                                                               clear                                                                               transparent                                                                           cloudy                                   after 24 hours unchanged                                                                            cloudy                                                                              cloudy                                                                              cloudy cloudy                                   pH value       9.3   9.2  9.1  9.2    9.1                                      1% strength in                                                                 distilled H.sub.2 O                                                            Corrosion resistance                                                           Herbert Test                                                                             0.5% rust  rust rust considerable                                                                          considerable                             DIN 51360/1                    rust   rust                                               1.0% no rust                                                                              trace of                                                                            trace of                                                                            rust   considerable                                                  rust rust        rust                                     Filter paper test                                                                        1.0% rust  rust rust rust   considerable                             DIN 51360/2                           rust                                               2.0% no rust                                                                              no rust                                                                             no rust                                                                             trace of                                                                              considerable                                                            rust   rust                                               2.5% no rust                                                                              no rust                                                                             no rust                                                                             no rust                                                                               rust                                     __________________________________________________________________________

                                      TABLE 3                                      __________________________________________________________________________     Formulation/example                                                                           1      2      3      A      B                                   __________________________________________________________________________     Product according to example                                                                  80 g   85 g   80 g   66 g   81 g                                Triethanolamine                                                                               5 g    5 g    5 g    15 g   4 g                                 Sodium hydroxide solution,                                                                    15 g   10 g   15 g   19 g   15 g                                40% strength                                                                   FORMULATION:                                                                   Na triethanolamine salt                                                                       24.0 g 24.0 g 24.0 g 24.0 g 24.0 g                              from example                                                                   Nonylphenol + 6 mol                                                                           6.8 g  6.8 g  6.8 g  6.8 g  6.8 g                               of ethylene oxide                                                              Distilled water                                                                               3.0 g  3.0 g  3.0 g  3.0 g  3.0 g                               Mineral oil    66.2 g 66.2 g 66.2 g 66.2 g 66.2 g                              Appearance at 20° C.                                                                   clear, clear, clear, milky, clear,                                             liquid liquid liquid cloudy liquid                              SOLUBILITY in distilled H.sub.2 O                                              immediately    milky  milky  milky  coarse milky                                                                          milky                               after 24 hours unchanged                                                                             cream  cream  separated                                                                             cream                               pH value       9.0    9.0    9.0    9.1    9.0                                 1% strength in distilled H.sub.2 O                                             CORROSION RESISTANCE                                                           Herbert Test                                                                             1.0% rust   considerable                                                                          rust          considerable                                              rust                 rust                                          2.0% rust   rust   rust          considerable                                                                   rust                                          3.0% no rust                                                                               trace of                                                                              no rust       considerable                                              rust                 rust                                Filter paper test                                                                        3.0% considerable                                                                          considerable                                                                          considerable  considerable                                       rust   rust   rust          rust                                          5.0% no rust                                                                               trace of                                                                              trace of      considerable                                              rust   rust          rust                                __________________________________________________________________________ 

We claim:
 1. A method for inhibiting corrosion of metals in contact with a cooling lubricant comprising the step of adding to said lubricant an effective amount of alkenylsuccinic acid of the formulae ##STR4## in which R denotes C₆ -C₁₈ alkenyl, R¹ denotes C₁₂ -C₁₈ alkyl, and M denotes a proton, an alkali metal ion or an ammonium ion of the formula NHR² R³ R⁴, and R², R³ and R⁴ are identical or different and denote hydrogen, C₁ -C₁₂ -alkyl, 2-hydroxyethyl or 2-hydroxypropyl.
 2. A method according to claim 1, wherein R denotes C₉ -C₁₂ -alkenyl.
 3. A method according to claim 1 wherein R¹ denotes C₁₂ -C₁₄ -alkyl.
 4. A method according to claim 1, wherein R² denotes C₁₂ -C₁₄ alkyl. 